Variable pitch propeller



'July'29,1941. w. w. EVERTS f 2,250,826

VARIABLE PITCH PROPLLER Filed March 11, 1939 2 Sheets-#Sheet l July 29, 1941. w. w. EVERTS 2,250,826

' VARIABLE FITCH PR01=1=':LL.ER Filed March 114, 19:59 sheets-smet 2 Patented July 29, 1941 VARIABLE rrrcn rnormnn Walter W. Everts, Baltimore, Md., asslgnor to Everel Propeller Corporation, Baltimore, Md., a corporation ol' Maryland Application March 11, 1939, Serial No.'261,323

6 Claims.

My invention relates rto propellers for air craft, boats, submarines, or the like.

An important object of the invention is to provide a propeller having a blade which is so pivotally mounted that the pitch of the blade is increased by rthe action of centrifugal force and this action is opposed by the action of the iluid medium in which the blade -is rotating, whereby the pitch of the blade automatically increases when the pressure of the uid medium decreases and the speed of rotation of the blade will remain substantially constant.

A further object of the invention is to provide means for mounting a non-metallic blade, such as a wooden blade, upon an attaching element, in such a manner as to prevent the creeping. of the blade upon the attaching element, against centrifugal force stresses.

A further object of the invention is to proyide a laminated woodenhpropeller, having the maximum tensile strength in that portion of the blade which receives the anchor element of the connecting. unit.

A further objectof the invention is to provide means for aiording the maximum binding blade again/stthe pulling action of centrifugal force.

A furtherobject of the invention is to provide coupling units for securely receiving and holding the connecting elements, and which coupling units are pivotally mounted upon the rotary element or hub.

A further object of the invention is to 'provide means whereby the central longitudinal axes of the blades are'arranged at an inclined angle with respect to the axes which the couplings turn. A

A further object of the invention is to provide a damping device for connecting theblades. to cause them to move as a unit when one blade is suddenly subjected to force, and subsequently of the pins upon allowing fthe blades to move separately, to vary of the airplane,

Figure 2 is an edge elevation of the same,

'strength between the anchor element and the section element and associated Figure 5 is a transverse section taken on line 5--5 of Figure 1,

Figure 46 is a longitudinal section taken on line 6-6 of Figure 2,

Figure 'I is avertical section taken on line 1-1 of Figure 1,

Figure 8 is a similar view taken on line 8 8 of Figure l,

Figure 9 is a. similar view taken on line 9-9 of Figure 1.

In the drawings, wherein for thelpurpose of illustration is shown a preferred embodiment of my invention, the numeral I0 designates the crank shaft of an internal combustion engine, mounted upon an airplane or theA like. Keyed to this shaft I0 for rotation therewithis a hub II, held against longitudinal displacement by a nut I2, as shown. The hub Il, see particularly Figure 6, has oppositely arranged radial pivot elements or pins I 3, preferably tubular.

The numeral I4 ldesignates a pairy of companion coupling members or yokes. Each of these coupling members or yokes is formed inI companion sections l5 and I5', having flat in-v ner contacting faces I6. The companion sec-V tions are secured together by bolts Il or the like. Each coupling member or yoke I4 has a bearing sleeve I8 at one end and a bearing sleeve I9 at its opposite end. These bearing sleeves receivev bronze bushings 20 and 2|, respectively. 'I'hese bronze bushings arel oating. As clearly shown in Figure 6, the sleeves I8 and I9 of the companion yokes are arranged in endeto-endrelation, the sleeve I8 .of one yoke being disposed outwardly of the sleeve I9 of the companion yoke. Each sleeve I9 has a raceway for receiving radial ball bearings 2|, engaging the bushing 29, and each pin or pivot element I3 carries an yend thrust'ball bearing 22, arranged between the-shoulder 23 and the shoulder 24 of the sleeve I9. It is thus seen that the'coupling members or yokes are pivotally mounted upon the pivot elements or pins I3, to turn thereon, but are radially extending portions are Jdisposed uponV opposite sides of the hub, as shown.

The numeral 26 designates connecting elements as a whole, for securing the blades to the coupling members or yokes I4. Each connecting element comprises a shank 21, which is preferably hollow, as shown in Figure 4. 'I'he shank has a flange 28, as shown. The shank is preferably circular in cross-section and is inserted in a socket 29, formed in the outer end of each coupling member or yoke I4, and the flange 28 is held within an annular groove 30. The shank is clamped in the socket 29 against turning movement. Particular attention is called to the fact that the socket 29 and the shank 26 held therein has its longitudinal axis arranged at an inclined or oblique angle with relation to the longitudinal axis of the adjacent pin I3. Each connecting element includes a iiat anchor element 3|, formed s integral therewith. This fiat anchor element is generally heart-shaped and tapers radially outwardly and has shoulders 32, at its inner end. The opposite sides of the flat anchor element 3| at their inner ends, are also connected with the shank 26 by tapered webs 33.

'I'he numeral 34 designates blades, preferably formed of wood. These blades are cut to produce the desired pitch. 'I'hese blades are of the conventional shape, having the leading faces convex or cambered. As stated, the longitudinal axes of the Shanks 21 are arranged at an oblique angle with respect to the longitudinal axes of the pins I3, and satisfactory results are obtained by having the axes of the shanks 21 disposed at an angle of about 25 degrees with respectto the longitudinal axes of the pins I3. It is preferred that the leading and trailing portions 35 and 36 of each propeller should be unbalanced with the trailing area larger.

As stated, the propeller blades are preferably formed of wood, and each blade comprises an inner ilat section 31, formed of a number of relatively thin layers or laminations of wood, glued together. This section is preferably built up as a unit separate from the remaining sections. The propeller comprises outer sections 38, formed of layers or strips 39 and 40, glued together. Each outer section is also preferably rst formed as a unit. The inner laminated section 31 formed of the relatively thin strips has the same thickness as the iiat anchor element 3|, and a recess 4| is f' cut in this inner laminated section 31, corresponding in shape and size to the anchor element 3| and the shank 21. The outer sections 38 of the propeller have inner recesses 42 formed there-A in, to receive portions of the shank 21 and the webs 33. The anchor element 3| has a relatively y large central opening 43, to receive a wooden slit plug 44, having the same thickness as the flat anchor element 3|. The anchor element 3| also has transverse openings 45, arranged in a triangular group to receive metal pins or plugs 46, having a driving flt therein, andv these pins or plugs also pass through openings 41 formed in the outer sections 33. In securing the connecting element with the propeller blade, one section 38 is arranged lowermost and the inner laminated section 31 arranged thereon and the anchor element 3| is then placed within theopening 4| of the inner laminated section 31. The upper section 38 is now placed upon the intermediate laminated section 31, these parts being so arranged that the openings 41 and 45 register. The wooden plug 44 has alsol been placed within the opening 43. I'he inner contacting surfaces of the sections 38 and the laminated section 31 and the plug are y suitably coated with glue and the thus assembled sections are then subjected to suitable pressure and maintained under this pressure until the glue has properly dried. The assembled sections are in the form of a rectangular block and after the sections have become properly glued together and dried the outer sections are then properly cut so that they produce the propeller blade of the desired shape. The pins ,48 are finally driven into the openings 45. I have found that I have thus obtained a. connection between the shank-21 and the blade which will securely hold the blade upon the shank so that the blade will not creep, due to radial thrust. This is important as it is well known that one of the disadvantages encountered in the use of the ordinary adjustable wooden propeller is that the inner ends of the bladeslcreep slightly in the metal sockets within which they are mounted, whichcauses the propeller to become unbalanced.

The coupling members or yokes I4 are interconnected by damping devices, arranged upon the leading side of the yokes. Each damping device comprises a cylinder 49 having its opposite ends provided with packing 50 and 5|, forming a gastight joint with a plunger rod 52. This plunger rod carries a plunger 53, having a contracted port 54. 'I'he cylinder 49 may be filled with air or with a liquid if desired. A tube is attached to the lower end of the cylinder 49 and this tube is pivotally connected with a pin 56 which in turn is secured to the lower yoke I4 near its inner end. The plunger rod 52 is pivotally connected with a pin 51, which is secured to the upper or companion yoke I4, near its outer end. The function of these damping devices is to cause the blades to move as a unit, when one blade is suddenly subjected to force or pressure, and subsequently permitting the blades to move separately to vary their pitch.

The operation of the propeller is as follows:

When the engine is started, the propeller is turned counterclockwise, viewed from the front of the airplane, which is the practice in the United States. As soon as the propeller rotates centrifugal force acting upon each blade 34 tends to move the same to the radial position. This action of centrifugal force is opposed by the air thrust, which tends to swing each blade upon the pivot I3 so that the outer end of the blade moves forwardly from the radial position. These two opposing forces act against each other and the blade will assume a normal operating position between the extreme forward position and the true radial position. Assuming the airplane is n ow flying at substantially sea level, the air thrust is at the maximum and the blade has its outer end moved forward slightly from the radial position, so that the blade will havey the mini-` mum pitch. When theA blade is turned upon its diagonal pivot I3. this lpivot being diagonal with respect to the central longitudinal axis 35' of the blade, it is also turned upon its longitudinal axis 35. thereby varying the pitch 4of the blade. The unbalanced areas 35 and 36 also aid in turning the blade about its longitudinal axis 35'.

When the blade turns upon the diagonal pivot I3 the longitudinal axis 35' of the blade swings about the surface of a cone. The action of centrifugal force tends to move the blade upon its pivot I3 to the true radial position, thereby increasing the pitch of the blade. Assuming that the propeller is being driven 2000 R. P. M. at sea'level, the

propeller will then have the minimum pitch for this elevation. If the airplane now rises to a conderably higher elevation, the resistance actin# upon the propeller will be reduced, while the action of centrifugal force would remain the same and hence the actionof centrifugal force would overcome the air thrust upon the propeller blade and the propeller blade would be turned upon its diagonal pivot I3 in a rearward direction, turning the blade about its longitudinal axis for increasing the pitch of the propeller. This increased pitch of the propeller will cause the propeller to drive the airplane at an increased speed' but the speed of rotation ofthe propeller will remain constant.

Having thus described my invention, what I claim is:

1. In a variable pitch propeller construction provided with propeller blades, a rotary member, a pivotal member xed to and extending radially from the rotary member, a pair of yokes journalled on the pivotal member, said yokes being onset from each other and extending radially beyond the pivotal member, a damping device connecting -the said yokes, a recess in the outer portion of each yoke, the longitudinal axis of said recess being at an inclinedv angle with relation to the longitudinal axis of the pivotal member, and a shank mounted in each recess, each shank connecting the yoke in which it is mounted to a blade of the propeller.

2. In a `variable pitch propeller construction provided with propeller blades, a rotary member, a pivotal member fixed to and extending radiallyv from the rotary member, a pairof yokes journalled on the pivotal member, said yokes being offset from one another and extending radially beyond the pivotal member, a damping device Cil connecting the said yokes, a recess in the outer portion of each yoke, thelongitudinal axis of said recess being at an inclined angle with relation to the longitudinal axis of the pivotal member, a

. shank mounted in each recess, each shank connecting a yoke with a blade of the propeller, the axis of each shank extending -longitudinally in respect to the longitudinal axis of the`recess in which it is mounted, each of said shanks com- .provided with propeller blades,a rotary member,

a pivotal member fixed toand extending radially from the rotary member, a pair of yokes journalled on the pivotal member, said yokes being effset from one another and extending radially beyond the pivotal member, a damping device connecting the said yokes, a shouldered recess in the outer por-tion of each yoke, the longitudinal axis of said recess being at an inclined angle of 25 per cent with relation to the longitudinal axis of the pivotal member, a shank mounted in each recess, each shank connecting the `yoke in whichit is mounted with a blade of the propeller, the vaxis of each shank extending longitudinally in respect to the axis of the recess in which it is mounted, each of said shanks comprising a root portion adapted to be carried within the recess and provided with a flanged portion which engages the shoulder of the recess, and an outer portion designed to be attached to the blade.

4. In a variable pitch propeller construction provided with propeller blades, a rotary member, a pivotal member fixed to and extending radially from the rotary member, a pair of yokes journalled on the `pivotal member, said yokes` being in end to end relation and offset from one another and extendingradially beyond the pvotal member, a damping device connecting the said yokes, each of said yokes comprising a pair of contacting faces secured together, a shouldered recess in the outer portion of each yoke, the longitudinal axis of said recess being at an inclined angle with relation tu the longitudinal axis of the pivotal member, a shank mounted in each recess, each'shank connecting the yoke in which it is mounted with a blade of the propeller, the axis of each shank extending longitudinally in respect to the axis of the recess in which it is mounted. each of said shanks comprising a root portion adapted to be carried within the recess, a flanged portion on each root portion designed to engage the shoulder of the recess, and an outer pori-ion designed to be attached to the blade.

5. In a variable pitch propeller construction provided with propeller blades, a rotary member, a pivotal member fixed to and extending radially from the rotary member, said pivotal member comprisingoiset shafts, a pair of yokes in end to end relation and offsetfrom one another and extending radially beyond the pivotal member, a damping device connecting the yokes, each of said yokes comprising a pair of contacting faces secured together and provided with a pair of sleeves in end to end relation which carry a bushing journalled on one of the shafts forming the pivotal member, whereby the yoke is rotatably mounted in respect to the shaft of the pivotal i member, the outer sleeve of each yoke being positioned exteriorly in respect to the inner sleeve of the companion yoke, a recess in the outer porv the longitudinal axis of the pivotal member, a

shank mounted vin each recess, each shank connecting a yoke with a blade of the propeller and the axis of each shank extending longitudinally in respect to the longitudinal axis of the recess.

in which it is mounted, each of said shanks comprising a root portion adapted to be carried within the recess and an outer portion being designed to be attached to the blade.

6. In a variable pitch propeller construction provided with propeller blades, a rotary member, a pivotal member xed to and extending radially from the rotary member, said pivotal member comprising offset shafts, and a shoulder on the inner extremity of each shaft, a pair of yokes in enti to end relation and oiset from one another and extending radially beyond the pivotal member, a damping device connecting' the yokes, each of said yokes comprising a pair of contactfing faces secured together and provided with a tatably mounted in respect to the shaft of the pivotal member, the outer sleeve of each yoke being positioned exteriorly in respect'to the inner sleeve of the companion yoke, a shouldered recess in the outer portion of each yoke, the longitudinal axis of the said recess being inclined at an angle with relation 'to the longitudinal axis .of the pivotal member, a shank mounted in each recess, each shank connecting a yoke with a blade of the propeller, and the axis of each shank extending longitudinally in respect tothe longitudinal axis of the recess in which it is mounted,

each of said `Shanks comprising a root portion defining a. plurality of apertures, means extendadapted to be carried within the recess, a flanged ing through the apertures to connect the plate portion on each root portion designed to engage member to the blade, and a, wedge-shaped web the shoulder of the recess, and an outer portion member connecting the root; portion and the said being designed to be attached to the blade, said 5 plate.

outer portion consisting of a flat plate member WALTER W. EVERTS. y 

